Impulsivity and clinical symptoms among adolescents with non-suicidal self-injury with or without attempted suicide

This study examined clinical characteristics and laboratory-measured impulsive behavior of adolescents engaging in either non-suicidal self-injury with (NSSI+SA; n=25) or without (NSSI-Only; n=31) suicide attempts. We hypothesized that adolescent with NSSI+SI would exhibit more severe clinical symptoms and higher levels of behavioral impulsivity compared to adolescents with NSSI-Only. Adolescents were recruited from an inpatient psychiatric hospital unit and the two groups were compared on demographic characteristics, psychopathology, self-reported clinical ratings, methods of non-suicidal self-injury, and two laboratory impulsivity measures. Primary evaluations were conducted during psychiatric hospitalization, and a subset of those tested during hospitalization was retested 4-6 weeks after discharge. During hospitalization, NSSI+SA patients reported worse depression, hopelessness, and impulsivity on standard clinical measures, and demonstrated elevated impulsivity on a reward-directed laboratory measure compared to NSSI-Only patients. In the follow-up analyses, depression, hopelessness, suicidal ideation, and laboratory impulsivity were improved for both groups, but the NSSI+SA group still exhibited significantly more depressive symptoms, hopelessness, and impulsivity than the NSSI-Only group. Risk assessments for adolescents with NSSI+SA should include consideration not only of the severity of clinical symptoms but of the current level impulsivity as well.

Distinctions in Behavioral Impulsivity: Implications for Substance Abuse Research

OBJECTIVES: Researchers have clearly implicated impulsivity as having a key role in substance use disorders, and comparisons of self-report measures suggest there are measurably different components of impulsive behavior. However comparatively little research has been devoted to understanding the multidimensional nature of this construct using laboratory measures of impulsivity that may be more sensitive to tracking changes across time. Many studies have measured impulsivity, but this construct has been measured using methodologically different types of laboratory impulsivity paradigms that are often used in isolation. As a result, it is important to determine whether some of the most frequently used types of behavioral measures of impulsivity account for unique variance. METHODS: Here, we used factor analytical techniques in two studies to evaluate the independence of three of the most commonly used behavioral impulsivity paradigms. First, a factor analysis was conducted using previously collected data (n = 204), and second, data was gathered specifically to replicate and extend the results of our original analysis (n = 198). RESULTS: Both studies revealed three distinct factors, confirming our hypothesis of at least three components of impulsive behavior that can be measured by these methodological approaches. CONCLUSIONS: These findings suggest that researchers should carefully consider their selection of laboratory-behavioral impulsivity measures, and that the measure(s) selected should be related to the particular underlying processes relevant to substance use disorders and treatment success.

Activation of liver tryptophan pyrrolase mediates the decrease in tryptophan availability to the brain after acute alcohol consumption by normal subjects

AIMS

We have previously suggested that acute ethanol consumption by normal subjects decreases the availability of circulating tryptophan (Trp) to the brain by activating liver Trp pyrrolase, the first and rate-limiting enzyme of the (major) kynurenine pathway of Trp degradation. The aim of the present study was to examine this hypothesis further by measuring plasma levels of kynurenine metabolites following alcohol consumption.

METHODS

After an overnight fast and a light breakfast, each of 10 healthy subjects received one of five drinks (placebo and doses of ethanol of 0.2, 0.4, 0.6 and 0.8 g/kg body weight in tonic water) on five different occasions. Blood samples were withdrawn 2 h later and plasma was analysed for concentrations Trp, competing amino acids (CAA) and kynurenine metabolites.

RESULTS

Along with the depletion of plasma Trp and the decrease in its availability to the brain, as expressed by the ratio of [Trp]/[CAA], plasma kynurenine was elevated by doses of ethanol of 0.2-0.8 g/kg body weight. The ratio% of [kynurenine]/[Trp], an index of the expression of Trp pyrrolase activity, was also increased by all doses of ethanol.

CONCLUSIONS

We conclude that activation of liver Trp pyrrolase mediates the depletion of plasma Trp and the decrease in its availability to the brain induced by acute ethanol consumption.

Differentiating impulsive and premeditated aggression: self and informant perspectives among adolescents with personality pathology

Previous research has articulated the conceptual differentiation of impulsive and premeditated aggression. Little, if any, of this research has examined personological differences among adolescents with aggression-oriented pathology, and little, if any, has examined both self and informant perspectives. The current study examined such differentiation within a Conduct Disorder population in which normal and pathological personality characteristics were examined via self- and informant-report. Results indicated the two forms of aggression were independent: high impulsive aggression was associated with high Neuroticism, but high premeditated aggression was associated with low Agreeableness and high Extraversion. Overall, adolescents high in impulsive aggression had a pattern of personality characteristics that are seen as socially-detached and emotionally volatile. In contrast, adolescents high in premeditated aggression had a pattern of characteristics seen as egocentric and socially-engaged but without concern for others. The results have implications for the social and motivational mechanisms producing the two forms of aggression.

A test of alcohol dose effects on multiple behavioral measures of impulsivity

BACKGROUND

Acute alcohol administration affects impulsive behavior, although these effects vary as a function of alcohol dose, assessment instrument, and time of measurement following administration.

METHODS

We concurrently examined the dose-dependent effects of alcohol on three distinct types of impulsivity tasks (continuous performance [IMT], stop-signal [GoStop], and delay-discounting [SKIP] tasks). Ninety healthy alcohol drinkers were assigned to one of the three task groups (n=30 each), each group experienced placebo, 0.2, 0.4, 0.6, and 0.8 g/kg alcohol doses across 5 experimental days, and task performance was assessed at 0.5h before and 0.25, 1.0, and 2.0 h after alcohol administration. We hypothesized that impulsive responding on all tasks would be increased by acute alcohol administration both across time and during the peak BrAC, but the magnitude would depend on the task being tested. Analyses included the time course and the peak BrAC effects. Task comparisons of peak behavioral changes following each dose are illustrated using standardized scores.

RESULTS

While alcohol consumption increased impulsive responding during all three tasks to some extent, our hypothesis was only partially supported. During the IMT, the 0.6 and 0.8 g/kg doses produced increased impulsive responding across time and at the peak BrAC. However, during the GoStop and SKIP, impulsivity increased across time regardless of the alcohol dose size, with no differences in impulsive responding among dose conditions at peak BrAC.

CONCLUSIONS

This study demonstrated alcohol-induced changes in impulsivity are not uniformly affected by alcohol. These data, in conjunction with previous studies, further support that impulsivity is not a unitary construct.

Comparison of 50- and 100-g L -tryptophan depletion and loading formulations for altering 5-HT synthesis: pharmacokinetics, side effects, and mood states

RATIONALE

Differences in 5-hydroxytryptamine (5-HT) function have been the subject of extensive research in psychiatric studies. Many studies have manipulated L -tryptophan (Trp) levels to temporarily decrease (depletion) or increase (loading) 5-HT synthesis. While most researchers have used a 100-g formulation, there has been ongoing interest in using smaller-sized formulations.

OBJECTIVES

This study examined the time course of multiple plasma indicators of brain 5-HT synthesis after a 50-g depletion and loading as a comparison to the corresponding 100-g formulations that are typically used.

MATERIALS AND METHODS

Plasma was collected from 112 healthy adults at seven hourly intervals after consumption of either a 50- or 100-g depletion or loading. Self-ratings of mood and somatic symptoms were completed before and after Trp manipulations.

RESULTS

The primary findings were that (1) the 50- and 100-g formulations produced the expected changes in plasma indicators after both depletion (-89% and -96%, respectively) and loading (+570% and +372%, respectively); (2) the 100-g depletion showed more robust effects at the 4, 5, and 6 h measurements than the 50-g depletion; (3) there was significant attrition after both the 100-g depletion and loading, but not after either of the 50-g formulations; and (4) both the 50- and 100-g depletions produced increases in negative self-ratings of mood and somatic symptoms, while loading significantly increased negative ratings after the 100 g only.

CONCLUSIONS

There are important considerations when choosing among formulation sizes for use in Trp manipulation studies, and the complete 7-h time-course data set of the typical plasma Trp measures presented here may help researchers decide which methodology best suits their needs.

The biphasic effects of alcohol: comparisons of subjective and objective measures of stimulation, sedation, and physical activity

BACKGROUND

Alcohol produces biphasic effects of both stimulation and sedation. Sensitivity to these effects may increase the risk for the development of alcoholism. Alcohol-induced changes in stimulation and sedation are commonly assessed with self-report questionnaires in human research and with physical activity monitoring in animal research. However, little is known about the effects of alcohol on physical activity or the relationship between physical activity and subjective self-report measures of stimulation and sedation following alcohol consumption in humans.

METHODS

Thirty healthy men and women (n = 15 each) from 21 to 38 years old completed daily measurements of physical activity and self-reports of stimulation and sedation following alcohol or placebo consumption. Across each of the four experimental days, all participants consumed a placebo, 0.4, 0.6, or 0.8 g/kg dose of 95% alcohol in a counterbalanced order. Breath alcohol concentrations, physical activity levels, and self-reported stimulation and sedation were measured at baseline and on the ascending and descending limbs of the breath alcohol concentration (BrAC) curve.

RESULTS

All alcohol doses increased physical activity, but these increases were time- and dose-dependent. Increases in physical activity lasted across both ascending and descending limbs of the BrAC curve. Following the 0.6 g/kg dose, both physical activity and self-reported stimulation increased during the ascending BrAC. Separate analyses of self-reported sedation scores indicated that alcohol consumption also increased sedation for the 0.6 and 0.8 g/kg doses. Physical activity was not significantly correlated with either self-reported stimulation or sedation at any time point.

CONCLUSIONS

These findings suggest that assessments of subjectively measured stimulation and sedation and objectively measured physical activity each assess unique aspects of the effects of alcohol. Used simultaneously, these measures may be useful for examining underlying mechanisms of the effects of alcohol on behavior.

Behavioral measures of impulsivity and the law

The General Theory of Crime proposes that crime is explained by the combination of situational opportunity and lack of self-control. Impulsivity is one of the important components of self-control. Because behavioral measures of impulsivity are becoming more commonly utilized to assess forensic populations, this manuscript provides an overview of three current behavioral measures. In doing so, an example of their application is provided using a group of individuals likely to come into contact with the legal system: adolescents with Conduct Disorder. Earlier age of onset of Conduct Disorder symptoms has been shown to be an important predictor of the persistence of poor outcomes into adulthood, including participation in criminal activities. This study found differential behavioral profiles across distinct measures of impulsivity by those with childhood- versus adolescent-onset Conduct Disorder. Legal implications for defining behavioral deficits using behavioral measures of impulsivity and their current limitations are discussed.